Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 211412
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
1012 AM EDT Tue Aug 21 2018

.SYNOPSIS...
Other than some patchy early morning fog another very nice day
is expected across much of the North Country with high pressure
over the region. Conditions will begin to deteriorate tonight as
an upper level trough of low pressure displaces the high
pressure and brings the return of rainfall to the region. Rain
will continue through Wednesday afternoon before exiting to the
east. Skies will clear heading into Thursday and will continue
to remain mostly clear through the first half of the weekend.
Temperatures will remain near normal with temperatures a degree
or two with each passing day.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 1010 AM EDT Tuesday...The forecast is on track this
morning so no changes were needed with this update.

Previous Discussion... Other than some high clouds over the
area early this morning and a little bit of fog...we should be
looking at a pretty good day. Deeper moisture associated with
the upper trough in the Upper Midwest is moving more north than
east and this feel any precipitation chances will be confined to
the late afternoon hours across portions of northern New York.
Strongest dynamic forcing associated with the upper trough will
lift more north into Canada tonight before upper trough axis
finally pushes east across the area Wednesday morning. As a
result...the best chances for precipitation will come tonight
across northern New York and then after midnight tonight through
midday on Wednesday for Vermont. Some instability will exist
later tonight into the first part of Wednesday and with enough
dynamic forcing cannot rule out the potential for some thunder
and have kept this idea in the forecast...but mainly just a
slight chance. Precipitation should start tapering off quickly
from west to east in the afternoon. Total rainfall amounts will
generally range from a third to two thirds of an inch. Highs
today will be in the mid 70s to lower 80s with lows staying in
the 60s with clouds and precipitation around. Highs on Wednesday
will generally be in the 70s.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY/...
As of 431 AM EDT Tuesday...As the cold front departs to our
east, a deep, drying northwesterly flow will become established
over the forecast area. Accordingly, showers will taper off
through the overnight hours. Clearing through the night may
result in the development of some patchy fog in some
climatologically favored locations, however northwesterly winds
just off the surface will work against widespread development.
Still, any sheltered areas that are able to decouple overnight
could see some mist/fog. The North Country will see a shot of
relatively cold air Wednesday night behind the departing system;
lows will generally be in the 40s to mid 50s.

Still on track for a very pleasant Thursday as high pressure
over the Central US shifts to the Mid-Atlantic. 925 mb temperatures
15-17C support highs generally in the mid to upper 70s. Mixing
of the boundary layer will transport drier air aloft down to the
surface, so expect a refreshing afternoon as dewpoints drop to
the 40s and a light northerly/northwesterly breeze is established.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 431 AM EDT Tuesday...Ridging builds in Thursday night and
remains in control through Friday night...keeping fair weather
in place to end out the work week. As the center of the surface
high shifts to the Mid-Atlantic, mid to upper-level flow will
becoming increasingly westerly and tap into warmer air from the
central US. This will allow for surface temperatures to warm
back up to the upper 70s/low 80s range. The ridge will shift
offshore over the weekend, while further upstream a closed low
from the northern Plains will become an open wave and lift
northeastward over eastern Canada/northeastern US. There remains
some uncertainty in the strength of the ridge and whether or
not the ridge will essentially deflect the wave`s energy to our
north or not. Thinking the ridge will keep us dry Saturday, but
models are starting to indicate the ridge may break down enough
to open the door to energy from the aforementioned shortwave
Sunday...resulting in the potential for some rain showers/weak
thunderstorms. Still much uncertainty in how this will play out.
Overall the general setup is not impressive; dynamics are weak,
moisture is increasing but nothing atypical for August values,
amount of instability able to be realized over the forecast area
is questionable... Have introduced some PoPs in the 20% to 35%
range Sunday, but will be able to better hone the forecast with
time.

Looking towards the next week, seeing signs of a large-scale
pattern change from the western US ridge/eastern US trough setup
that has dominated the latter half of our summer thus far.
Broad ridging looks to encompass the southern half of the United
States by Monday, allowing the general weather pattern to
become increasingly progressive over the northern tier of the
country. Thus, have kept precipitation chances in the 15% to 40%
range for Monday and Tuesday.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
Through 12z Wednesday...Looking at VFR conditions through 00z
with mainly only mid and high level clouds expected to move
across the area. The only exception to this will be some early
morning fog at KMPV...which will result in some MVFR to LIFR
conditions for brief periods between 12z and 14z. South to
southwest winds will be increase today with gusts in the 10 to
20 knot range. Lower ceilings should move in after 00z with MVFR
conditions expected. Rain showers will also start to move in
after 00z...but visibilities will generally be in the VFR
category. Lower ceilings and visibilities are expected after
06z...generally looking at MVFR to IFR conditions between 09z
and 12z.

Outlook...

Wednesday: Mainly VFR, with local IFR possible. Chance SHRA,
Slight chance TSRA.
Wednesday Night: VFR. Slight chance SHRA.
Thursday: VFR. NO SIG WX.
Thursday Night: VFR. NO SIG WX.
Friday: VFR. NO SIG WX.
Friday Night: VFR. NO SIG WX.
Saturday: VFR. NO SIG WX.

&&

.MARINE...
A lake wind advisory is in effect for tonight through Wednesday
as south winds increase into the 15 to 25 knot range tonight...then
shift to the west Wednesday afternoon. Winds of this magnitude
will create waves of 3 to 5 feet and rather choppy
conditions...especially over the northern half of Lake Champlain
tonight and then the east side of the lake on Wednesday once the
winds shift to the west.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.

&&

$$
SYNOPSIS...Evenson
NEAR TERM...Evenson/Hastings
SHORT TERM...RSD
LONG TERM...RSD
AVIATION...Evenson
MARINE...Evenson



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